Bifocals are eyeglasses, commonly prescribed for presbyopia, with two distinct optical powers.
Although there are arguments against him, Benjamin Franklin is generally credited with the invention of bifocals. After a correspondence between George Whatley and John Fenno it was thought that Franklin possibly invented the bifocals fifty years earlier than previously thought. Many inventions are worked on independently by many people and bifocals may have been the same, however, Franklin was...